Suggestion: Add WasmMsg::UpdateAdmin to transfer migration ownership to other address

[yun-yeo]

Currently there is no way to transfer contract migration ownership to other address, if the admin is a contract.

It would be great to have some interface to transfer migration privilege to other address.

[ethanfrey]

When we add this, let's add ClearAdmin as well.

I think we decided to make one with String and other with no field, rather than using Option<String> for the public messages. I would keep the same here, unless there is a strong objection.

[webmaster128]

Good point, @ethanfrey. Let's make the messages match the wasmd types:

// MsgUpdateAdmin sets a new admin for a smart contract
message MsgUpdateAdmin {
  // Sender is the that actor that signed the messages
  string sender = 1;
  // NewAdmin address to be set
  string new_admin = 2;
  // Contract is the address of the smart contract
  string contract = 3;
}

// MsgClearAdmin removes any admin stored for a smart contract
message MsgClearAdmin {
  // Sender is the that actor that signed the messages
  string sender = 1;
  // Contract is the address of the smart contract
  string contract = 3;
}

I think we decided to split it in two message types to make clearing admin very explicit.